Operationalized releases of wAlbB Wolbachia in Aedes aegypti lead to sharp decreases in dengue incidence dependent on Wolbachia frequency

In Aedes aegypti mosquitoes, introduction of certain strains of inherited Wolbachia symbionts results in transmission blocking of various viruses of public health importance, including dengue. This has resulted in a replacement strategy for dengue control involving release of male and female mosquitoes, whereupon Wolbachia is able to spread through Ae. aegypti populations to high frequency and reduces the incidence of dengue. Wolbachia strain wAlbB is an effective transmission blocker and stable at high temperatures, making it very suitable for use in hot tropical climates. Following the first trial field releases of the wAlbB strain in Ae. aegypti in Malaysia, releases of wAlbB Ae. aegypti have for the first time become operationalized by the Malaysian health authorities. We report here on changes in dengue incidence based on a set of 20 releases sites and 76 control sites in high rise residential areas, which allows us to directly assess the impact of Wolbachia frequency on dengue incidence. The results indicate an average reduction in dengue of 62.4% (confidence intervals 50-71%); importantly the level of suppression increased with Wolbachia frequency, with suppression of 75.8% (confidence intervals 61-87%) estimated at 100% Wolbachia frequency. These findings emphasize the large impacts of wAlbB Wolbachia invasions on dengue incidence in an operational setting, with the expectation that the level of dengue will further decrease as wider areas are invaded.